Cryoelectric power system

ABSTRACT

A cryoelectric power system for use in application(s) in which a conventional internal combustion engine is used. The power system includes a source of cryogenic fuel, a cryoelectric boiler for vaporizing the cryogenic fuel, a heat exchanger for warming the vapor, and two or more turboalternators, each turboalternator generating electricity. This power system may be utilized either as the primary power source or as secondary pending the needs of the application or location of the power requirement. The Seebeck and Ettingshausen effects may be utilized in the thermoelectric boiler, thereby producing additional electricity, and the electricity produced by the cryoelectric boiler and the turboalternators is output to appropriate controls and circuitry where it may be summed and used to power an electric power system. Superconductive material may be used in the manufacture of the turboalternators and magnetic coil for additional system enhancement. The resulting, highly efficient, power system is used to advantage in, for instance, for powering a non-polluting automobile or as a prime mover for providing a wide array of commercial electrical services or for driving a wide variety of industrial electrical systems.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to the use of a cryogen as a fuel for a prime mover. In more detail, the present invention relates to improvements on the device disclosed in U.S. Pat. No. 4,311,917, which prior patent is incorporated into this disclosure in its entirety as if fully set forth herein.

[0002] The finite quantity of hydrocarbon fuels that are available, the cost of such fuels, and the pollutants produced by combustion of such fuels together indicate that it is necessary to develop alternatives to the power sources in current widespread use. One alternative that has been investigated is the use of cryogenic heat engines, a concept in which a cryogenic substance is used as a heat sink for a heat engine. Examples of such engines include those that utilize liquid nitrogen to propel the vehicles that were designed and built at the University of North Texas and the University of Washington. In the engines of both of these vehicles, liquid nitrogen is vaporized and then expanded through an expansion engine to produce work.

[0003] The above-incorporated U.S. Pat. No. 4,311,917 discloses a motor that operates in much the same fashion, but which utilizes the work output from an expansion engine to drive a generator that either powers an electric motor or charges a battery pack. That patent discloses the advantage of cooling the generator and the motor with the cryogenic gas so as to improve the performance characteristics of these components. There is, however, a need for improvements in the efficiency of the power system disclosed in that patent, and it is a primary object of the present invention to provide such improvements in the apparatus disclosed in that prior U.S. Pat. No. 4,311,917.

[0004] Another object of the present invention is to provide an alternative to the internal combustion engine that provides sufficient power output to be useful as a prime mover for providing power in many industrial and consumer applications. The power from the prime mover is utilized in industrial applications, in remote locations, back-up power systems for hospitals and other facilities, as a primary power system in locations in which emissions must be controlled, in the automotive industry and for other vehicles, for instance, as a non-polluting automobile or other motorized vehicle such as industrial trucks and refrigeration units, to run the lights and refrigeration systems of vehicles that would normally draw against the vehicle's electrical system, as a secondary power source in an electrical or hybrid vehicle, and as a charging system for electrical or hybrid vehicles so that the batteries of the vehicle are charged while the vehicle is in use or parked.

[0005] Another object of the present invention is to provide a cryoelectric power system that utilizes a turbo-alternator producing AC or DC voltage in place of known alternator circuits, thereby reducing the size of the system while retaining, and even increasing, the power output of the power system.

[0006] Another object of the present invention is to provide a cryoelectric power system utilizing superconductive materials for enhancing electrical efficiency and increasing electrical output over prior cryoelectric power systems.

[0007] Another object of the present invention is to provide a cryoelectric power system that operates virtually frost-free by utilizing a flow of warmed cryogen to flow across the heat exchangers and a cryogenic boiler to enhance the efficiency of the expansion of the cryogen and reduce, or even eliminate, frost accumulation.

[0008] Another object of the present invention is to provide a cryoelectric power system that utilizes one or more heat exchangers for enhancing the efficiency of the of the system by warming the cryogen to a high pressure vapor, reducing the size of the re-heat stages (as compared to prior known systems) and clearing (or keeping clear) one or more sections of the cryoelectric power system of frost.

[0009] Another object of the present invention is to provide a cryoelectric power system with enhanced efficiency in the generation of DC power by utilizing one or more thermodynamic phenomena, such as the Seebeck and/or Ettingshausen effects.

[0010] Yet another object of the present invention is to provide a cryoelectric power system that produces electricity at higher efficiency than prior cryoelectric power systems by further enhancing power output by utilizing the Ettingshausen effect.

[0011] Another object of the present invention is to provide a cryoelectric power system that produces electricity at a higher efficiency than prior power systems by using regenerative processes to enhance the expansion of a cryogenic fuel, such as liquid nitrogen, to high pressure vapor for the purpose of driving (fueling) one or more turboalternators to generate electricity.

[0012] Other objects, and the advantages of the invention, will be made clear to those skilled in the art by the following description of a preferred embodiment of an apparatus constructed in accordance with the teachings of the present invention and methods of utilizing those teachings.

SUMMARY OF THE INVENTION

[0013] These objects, and the advantages of the cryoelectric power system of the present invention, are met by providing a source of cryogenic fuel, a cryogenic boiler for vaporizing the cryogenic fuel, a heat exchanger for increasing the temperature of the vaporized fuel to expand and increase the volume of the vapor, and at least two turboalternators driven by the vapor output from the boiler to generate electricity, the turboalternators being located in such proximity to the source of cryogenic fuel as to be maintained at a temperature selected to improve the efficiency of the turboalternators. The turboalternators may be arranged in series so that they are each driven by the exhaust from the previous turboalternator to maintain maximum use and efficiency of the expanding cryogenic fuel. The windings of the turboalternators are preferably comprised of super-conducting materials and are located in close enough proximity to the cryogenic fuel source as to be maintained at a temperature selected to improve the performance of the alternator, and therefore, the efficiency and output of the cryoelectric power system. Optionally, the turboalternators are arranged in parallel from a manifold located between the heat exchanger and the turboalternators such that the expanding cryogenic fuel is heated and expanded just once.

[0014] In the case of a cryoelectric power system that includes parallel turboalternators, the use of two or more turboalternators allows for a corresponding number of individual power circuits via common electrical circuit connections or they can be phased so as to produce three-phase power for larger and more complex AC electrical power needs. Further, the individual power circuits can be synchronized together so as to produce a single, high wattage output that can be utilized to feed into an electrical utility network to provide power to the power grid or for other industrial applications.

[0015] The efficiency of the cryoelectric power system of the present invention is further enhanced by providing means for generating electricity from the increase in the temperature of the cryogenic fuel entering the boiler and the vaporized cryogenic fuel exhausted from the turbines. The electricity produced by both the generating means and the turboalternators is summed and output for the particular desired application, which may be as a prime mover for a wide variety of electrically driven systems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a schematic diagram of a preferred embodiment of a cryoelectric power system constructed in accordance with the teachings of the present invention.

[0017]FIG. 2 is a schematic diagram of a second preferred embodiment of a cryoelectric power system constructed in accordance with the teachings of the present invention.

[0018]FIG. 3 is a longitudinal sectional view, shown in schematic illustration, of a thermoelectric boiler of a type suitable for use in connection with the cryoelectric power systems of either FIGS. 1 or 2.

[0019]FIG. 4 is a cross-sectional view of the thermoelectric boiler of FIG. 3 taken along the lines 4-4 in FIG. 3.

[0020]FIG. 5 is a longitudinal sectional view, shown in schematic illustration, of a cryoelectric boiler of a type suitable for use in connection with the cryoelectric power systems of either FIGS. 1 or 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0021] Referring first to FIG. 1 of the accompanying drawings, a schematic drawing of a preferred embodiment of a cryoelectric power system constructed in accordance with the teachings of the present invention is shown. In the particular embodiment shown, the cryoelectric power system includes a source of cryogenic fuel in the form of a cryogenic tank 10 and cryogenic pump 12 for pressurizing the liquid cryogenic fuel from the tank 10. The cryogenic fuel is preferably liquid nitrogen (LN₂), but those skilled in the art will recognize from this disclosure that other cryogens, such as liquid air, are available that provide the extreme cold that allows their use as a cryogenic fuel that is suitable for use in connection with the present invention. Liquid Nitrogen (LN2) has been selected as the primary fuel due to its favorable expansion properties, because it is 100% non-polluting and is 100% non-flammable, and because it is extracted from the breathable air and is returned to the atmosphere as the exhaust (warmed nitrogen vapor) of the present invention. Other cryogens, including liquified air; helium and hydrogen, may optionally be used as the primary fuel. The cost, availability and efficiencies of the cryogenic fuel will vary on the cryogen or combinations of cryogens selected as the fuel. An external storage tank 14 is shown, with a pump 24 for pressurizing the cryogenic fuel from storage tank 14 to cryogenic tank 10, that may be an on-site tank, a railroad car, truck trailer, or other source of cryogenic fuel as known in the art.

[0022] The cryogenic fuel exits cryogenic tank 10 through a pump 24 and is vaporized in a cryoelectric boiler 16, which takes the form of a thermoelectric boiler (TEB) in the particular embodiment shown. Appropriate flow and pressure controls 12, as well as flow, pressure, and temperature sensors (not shown), are located at appropriate locations as needed to balance the flow of the cryogen and the expanded vapor as known in the art.

[0023] The primary warming of the vaporized cryogen occurs in the high pressure heat exchanger 20 that is preferably located in a dry gas enclosure, or frost-free chamber, 18 which, like the alternators 26 and boiler 16, is described in more detail below. The pressurized cryogenic vapor exits the thermoelectric boiler 16 to a high pressure heat exchanger 20 and then passes through one or more heat exchanger/turboalternator sets, each operating at progressively lower pressures, all of which may be contained within an enclosure 22 through which the warmed, expanded vapor (exhaust) is circulated internally before being exhausted to line 38 and eventually to the atmosphere. In the preferred embodiment shown in FIG. 1, a series of three heat exchanger/turbines is provided, the vapor exiting the high pressure heat exchanger 20 to a high pressure turboalternator 26 through line 28, to an intermediate heat exchanger 30, intermediate pressure turboalternator 32, low pressure heat exchanger 34, low pressure turboalternator 36, and out into the enclosure 22 from the final turboalternator 36. Vapor exiting the enclosure 22 is routed through line 38 to the dry gas enclosure 18 for reducing frost formation around thermoelectric boiler 16 and high pressure heat exchanger 20, and then vented to the atmosphere. A baffle 72 may be provided in the enclosure 18 (see FIGS. 3 and 5) to insure even distribution of the warm gas within enclosure 18.

[0024] In the embodiment shown in FIG. 2, in which like structure is denominated with the same reference numerals as utilized in FIG. 1 but preceded by a “2,” the high pressure vapor exiting the thermoelectric boiler 216 through line 228 passes through the high pressure heat exchanger 220. The vapor exits heat exchanger 220 to a manifold 250 that distributes the high pressure vapor stream to one or more turboalternators (AC or DC), three being shown at reference numerals 230A, 230B, and 230C in FIG. 2, and out of the turboalternators 230 to be rewarmed and circulated over the high pressure heat exchanger before exhausting to the atmosphere.

[0025] The electrical output from each of the turboalternators 26, 32, and 36, or 230A, 230B, and 230C, is routed through a lead 40 (or 240) to the power terminal block 48 (or 248), preferably located proximate control panel 44/244. Similarly, the electrical output from thermoelectric boiler 16/216 is routed through lead 45 to the power terminal block 42, where it is summed with the output of turboalternators 26, 32, and 36 or 230A, 230B, and 230C. The output from TEB 16/216 is DC power whereas the output from turboalternators 26, 32, and 36, or 230A, 230B, and 230C is either AC or DC, hence separate terminal blocks 42 and 48 are shown, but those skilled in the art who have the benefit of this disclosure will recognize that separate terminal blocks are not necessary depending upon the particular electrical power output that is desired. Control panel 44/244 is provided with appropriate controls, indicated generally at reference numeral 46/246, for system main on/off, control of voltage, amperage, frequency, rpm, pressure and temperature monitoring and control, and monitoring and control of output power (for instance, in watts), all accomplished in accordance with principles known in the art.

[0026] In the preferred embodiments shown in FIGS. 1 and 2, the cryogenic boiler 16 is provided with means for generating electricity from the temperature difference of the cryogenic fuel entering the cryogenic boiler and the vaporized cryogenic fuel exiting the turbines and reheated to near atmospheric termperatures. In the embodiments shown, the generating means takes the form of a layer of thermoelectric (TE) material 74 positioned adjacent the cryoelectric boiler 16 (hence the references herein to a thermoelectric boiler (TEB)). The TEB 16 of the present invention is shown schematically and in more detail in FIG. 3 and generates DC voltage/current. The use of such a boiler in connection with the cryoelectric power system of the present invention increases the power production of the cryoelectric power system by as much as 4-6%, depending upon such factors as the particular cryogenic fuel being utilized, the output of the turboaltemators, being either or both AC or DC power, and the presence of a magnetic field.

[0027] As shown in FIGS. 3 and 4, TEB 16 is comprised of a shell 60, preferably made of stainless steel or aluminum, having a magnet coil 62 mounted in a sleeve 64 that is commonly retained therein. A flanged coupling 66 to lid 68 is provided so that the sleeve 64 in which the magnet 62 is mounted can be removed from the shell 60 for maintenance. The shell 60 is shown enclosed by the dry gas enclosure 18, the dry gas that is routed through enclosure 18 being, of course, the vapor exiting the last (low pressure) turbine 36 as shown in FIG. 1, for preventing frost formation therein.

[0028] The shell 60 of TEB 16 is surrounded by layers of very thin electrical insulation 70 sandwiching a TE material 74 comprised of, for instance, Bi₂Te₃-Bi₂Se₃Te₃ having electrically conductive straps 76 alternately connecting the TE material, for generating electricity from the temperature difference between the cryogen in shell 60 and the ambient temperature in accordance with the Seebeck effect. The shell 60 is preferably oriented vertically so that the cryogen entering shell 60 receives heat and causes the liquid cryogen to vaporize and rise through the shell 60 to exit at the top of the shell.

[0029] The Seebeck effect occurs when the Bi₂Te₃-Bi₂Se₃Te₃ comprising TE material 74 is exposed to the difference in temperature between the inside of shell 60 and the ambient air outside of shell 60. Thus, TEB 16 produces electricity that is delivered to the output leads 45 through the conductive straps 76. The figure of merit of the TE material is increased by a factor of approximately two by the presence of a magnetic field such as is produced by the magnet 62 located in shell 60, and in the embodiment shown, means is provided for applying a magnetic field to the TE material 74 in the form of electromagnetic coils, comprised of copper or superconductive wiring, for additional power output from TEB 16 by utilizing the Ettingshausen effect. The Ettingshausen effect requires a concurrent magnetic field of approximately 0.5 Tesla parallel to the heat flow of the TE material 74 and a difference in the temperature from the atmosphere outside the TEB to the cryogenic fuel passing through TEB 16. Power is provided to the electromagnetic coil 62 through leads A, B.

[0030] Although each of the embodiments of the cryoelectric power system of the present invention shown in FIGS. 1 and 2 utilize the Seebeck effect to generate electricity with a TEB 16, it will be recognized by those skilled in the art that the cryoelectric system need not utilize the Seebeck effect to provide an advantage in efficiency over prior known cryoelectric systems. The vaporization of the cryogen in the boiler 16, followed by the warming of the vapor in heat exchanger 20, provides sufficient volume to drive the turboalternators in a manner that is highly efficient. It has been found that an operating range of from about 200 psig to about 500 psig (measured at the output from heat exchanger 20) provides this advantage, and this operating range can be achieved by commercial cryogenic pumps. Sufficient warming can be achieved by the exchange of heat with the atmosphere around boiler 16, and referring now to the embodiment of the boiler 16 shown in FIG. 5, it can be seen that heat fins 80 are provided to facilitate this exchange of heat with the atmosphere. No TE material is shown in FIG. 5 because the function of the boiler shown in that figure is to facilitate expansion of the vaporized cryogenic fuel, but those skilled in the art will recognize that a thermoelectric boiler such as is shown in FIGS. 1-4 can also be provided with fins 80 for this same purpose.

[0031] The turboalternators 26, 32, and 36 (230A, 230B, and 230C in FIG. 2) will now be described in detail. Conventional hot gas-fueled turbine generator sets consist of a high-speed turbine (e.g., 25-50 k rpm) coupled to a low speed electrical generator (e.g., 1.5 k to 3 k rpm) through a reduction gearbox, whereby the gear reduction process produces extra losses. However, the voltage output of such a generator is proportional to its rotational speed. Consequently, if an alternator is run at turbine speed and is small enough to be integrated onto the same shaft as the turbine, the result is a compact, high-speed generator, or turboalternator. Each of the turbines 26, 32, and 36 (and 230) is constructed in this fashion. Such turboalternators are available commercially from several sources, including Bowman Power Limited (Southampton, England), Stewart & Stevenson (Houston, Tex.), Pratt & Whitney (East Hartford, Conn.), Baldor Electric Company (Fort Smith, Ark), Barber-Nichols, Inc. (Arvada, Calif.), Airworld (UK), Ltd. (Winslow Bucks, UK), and Hess Microgen, LLC/Integrated Power Systems International (Rochester, N.Y.), in varying operating ranges and outputs. In the case of the present invention, the operating ranges and outputs of the turboalternators are sized to the corresponding heat exchangers 20, 30, and 34 as the cryogenic fuel is warmed by the heat exchangers, thereby maximizing their respective electrical outputs to the power terminal block 42. Those skilled in the art who have the benefit of this disclosure will recognize that the number of such turboalternators utilized in connection with the cryoelectric power system of the present invention, and their sizing, will involve optimization in accordance with principles known in the art.

[0032] As shown in FIGS. 1 and 2, each of the turboalternators 26, 32, and 36, and 230A, 230B, and 230C, is positioned relative to tank 10 so that the alternator, directly attached to the turbine shaft, is closely situated to tank 10 so that the cold temperature of the cryogenic fuel increases the operating efficiency of the alternator, especially if superconductive materials are utilized in the windings of the alternator. Specifically, the turboalternators 26, 32, and 36, and 230A, 230B, and 230C, are mounted in complementary-shaped mounts 52/252 that are received in the wall of tank 10.

[0033] The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching without deviating from the spirit and the scope of the invention. The embodiment described is selected to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as suited to the particular purpose contemplated. For instance, it will be recognized that the electrical output of the turboalternators may need to be synchronized with the output from the thermoelectric boiler and/or super-conducting alternator. Alternatively, each of the electrical power outputs is utilized independently of the other such that there is no need for synchronization. All such changes are intended to fall within the scope of the invention as defined by the claims appended hereto. 

What is claimed is:
 1. A cryoelectric power system comprising: a source of cryogenic fuel; a cryogenic boiler in which the cryogenic fuel is vaporized; a heat exchanger to increase the temperature of the vaporized cryogenic fuel; and one or more turboalternators driven by the high pressure vapor to generate electricity, said turboalternators being located in such proximity to said source of cryogenic fuel as to be maintained at a temperature selected to improve the efficiency of said turboalternators.
 2. The cryoelectric power system of claim 1 wherein said turboalternators are connected in series so that the vapor output from one of said turboalternators is input to the next of said turboalternators.
 3. The cryoelectric power system of claim 1 additionally comprising a manifold between said heat exchanger and said turboalternators for distributing the vapor to said turboalternators.
 4. The cryoelectric power system of claim 1 additionally comprising an enclosure in which said cryogenic boiler is located and the vapor exiting said turboalternators passes through said enclosure for reducing the accumulation of frost around said cryogenic boiler.
 5. The cryoelectric power system of claim 1 wherein said boiler is provided with means for generating electricity from the difference in the temperature of the cryogenic fuel in said cryogenic boiler and the temperature outside said cryogenic boiler.
 6. The cryoelectric power system of claim 5 wherein said generating means additionally comprises means for exchanging heat between the vaporized cryogenic fuel inside the cryogenic boiler and the ambient temperature outside said cryogenic boiler.
 7. The cryoelectric power system of claim 5 wherein the electricity generated by said generating means and the electricity produced by said turboalternators is summed.
 8. The cryoelectric power system of claim 5 wherein said generating means comprises a layer of thermoelectric material positioned adjacent said cryogenic boiler for producing electricity from the temperature difference between the vaporized cryogenic fuel inside said cryogenic boiler and the ambient temperature outside said cryogenic boiler.
 9. The cryoelectric power system of claim 8 additionally comprising means for applying a magnetic field to said layer of thermoelectric material.
 10. The cryoelectric power system of claim 9 wherein said means for applying a magnetic field is positioned inside said boiler.
 11. The cryoelectric power system of claim 5 additionally comprising means for increasing the electrical output of said generating means by utilizing the Ettingshausen effect.
 12. A method of generating electricity from cryogenic fuel comprising the steps of: pumping a cryogenic fuel from a storage tank; utilizing the Seebeck effect to generate electricity from the difference in the temperature of the cryogenic fuel and the ambient temperature; warming the cryogenic fuel through one or more heat exchangers; driving a turboalternator with the warmed cryogenic fuel to generate electricity; and summing the electricity produced by the Seebeck effect and the electricity generated by the turboalternators.
 13. The method of claim 12 wherein the cryogenic fuel is vaporized in a thermoelectric boiler.
 14. The method of claim 12 additionally comprising utilizing the expanded cryogenic fuel to reduce the accumulation of frost on the thermoelectric boiler.
 15. The method of claim 12 additionally comprising venting the expanded vapor to the atmosphere.
 16. The method of claim 12 additionally comprising applying a magnetic field to the thermoelectric boiler.
 17. A method of generating electricity from a cryogenic liquid comprising the steps of: heating the cryogenic liquid to change the cryogenic liquid from a liquid to a vapor; increasing the volume of the vapor in one or more heat exchangers to an operating range of from about 200 to about 500 psig; and driving at least one or more turboalternators with the expanded vapor to generate electricity.
 18. The method of claim 17 additionally comprising utilizing the Seebeck effect to produce electricity from a difference in the temperature of the cryogenic liquid and ambient temperature.
 19. The method of claim 18 additionally comprising summing the electricity generated by the turboalternators and the electricity produced by utilizing the Seebeck effect. 